1. Field of the Invention
The present invention relates to a musical tone synthesizing apparatus which synthesizes musical tones of stringed instrument, percussion instrument and the like.
2. Prior Art
As the well-known conventional musical tone synthesizing apparatus, there is provided a so-called waveform-memory-type musical synthesizer which memorizes several kinds of musical tone waveforms generated from non-electronic musical instruments in a waveform memory, wherein such musical tone waveforms are digitized by effecting the Pulse Code Modulation (PCM). This synthesizer reads digital data corresponding to designated performance information from the waveform memory and then reproduces the musical tone waveform. In general, the non-electronic musical instrument (hereinafter, simply referred to as the acoustic musical instrument) can generate the musical tones full of variety in response to the performance. For example, in case of the wind instrument, the tone color can be slightly varied by varying the blowing pressure applied to its mouth-piece. Therefore, in order to reproduce a plenty of musical tone waveforms by the conventional waveform-memory-type musical synthesizer, quite a large amount of storage capacity must be required for the waveform memory, which affects the operation and construction of the musical synthesizer. Meanwhile, it is possible to reproduce the musical tone waveforms full of variety by mixing plural musical tone waveforms together by effecting the computation or modulation. However, when mixing the musical tone waveforms, the quantity of the operation must be large, which affects the operation of the musical synthesizer.
Thus, there is proposed a musical tone synthesizing apparatus using the electric simulation model which simulates the tone-generation mechanism of the acoustic musical instrument. Herein, by activating such simulation model, it is possible to synthesize the desirable musical tone. For example, as the simulation model of the string-striking instrument such as the piano, the musical tone synthesizing apparatus provides a closed-loop including a delay circuit simulating the propagation delay of the string vibration and a low-pass filter simulating the acoustic loss to be occurred at the string. In the above-mentioned musical tone synthesizing apparatus, the closed-loop is applied with an impulse signal representative of the impulse which is occurred when the hammer strikes the string, and then the closed-loop is subject to the resonance state. Thereafter, the signal circulating the closed-loop is picked up as the musical tone signal. Thus, this apparatus can accurately simulate the phenomenon in which the standing-wave vibration of the string is produced when the hammer strikes the string. Then, such standing-wave vibration of the string is directly radiated into the air so that the musical tone is generated with accuracy. For convenience' sake, such musical tone is called as "direct sound" because it is generated by directly radiating the standing-wave vibration of the string.
In the actual acoustic musical instrument, there is provided a resonator (e.g., acoustic plate of piano, casing of guitar). Therefore, by use of the resonator which resonates the above-mentioned direct sound, the acoustic musical instrument can generate the resonant sound.
Thus, Japanese Paten Publication No. 1-15074 discloses the musical tone synthesizing apparatus capable of reproducing both of the direct sound and resonant sound. In order to reproduce both sounds, this apparatus provides two waveform memories wherein one memory memorizes direct sound waveforms and another memory memorizes resonant sound waveforms. In response to the performance information, both of the direct sound waveform and resonant sound waveform are read out and then mixed together.
Meanwhile, in the string-striking instrument such as the piano, the impulse occurred when the hammer strikes the string propagates toward the acoustic plate so that the resonant sound corresponding to the impulse is to be generated. In case of the stringed instrument such as the guitar, the impulse to be applied to the string by the pick or finger nail is transmitted toward the casing via the bridge portion so that the resonant sound corresponding to the impulse is to be generated. In short, the actual acoustic instrument generates three kinds of sounds, i.e., the direct sound which is generated by directly radiating the standing-wave vibration, resonant sound to be generated from the resonator in accordance with the direct sound and another resonant sound which is generated when the impulse to be applied to the instrument when playing such instrument propagates toward the resonator (hereinafter, such another resonant sound will be referred to as "transient sound"). Then, these three kinds of sounds are mixed together to produce the musical tone, which will be heard by the audience. However, the conventional musical tone synthesizing apparatus can reproduce the above-mentioned direct sound and the resonant sound corresponding to the direct sound but cannot reproduce the transient sound to be generated based on the impulse applied to the instrument when playing the instrument. Thus, there in a problem in that the conventional apparatus cannot reproduce the acoustic sounds of the instruments with accuracy.
In order to eliminate the above-mentioned problem, it is possible to employ the provision of another waveform memory which memorizes the transient sounds picked up from the instruments. In this case, such memorized transient sounds are mixed together with the direct sounds and resonant sounds. However, it is very difficult to pick up such transient sounds from the instruments by the conventional technique. Although such pick-up process of picking up the transient sounds requires much effort, it is impossible to obtain the sufficient transient sounds. When reproducing the transient sounds by the sound source employing the PCM method, the sound quality must depend on the recording accuracy. In some cases, the reproduced transient sounds may offend the ears of the audience.
In the meantime, as known well, a plenty of acoustic musical instruments provide the resonators each of which is used to efficiently radiate the vibration into the air. For example, the piano provides the acoustic plate and guitar provides the casing as the resonator. In short, in the acoustic musical instrument providing the resonator, the string vibration is maintained and efficiently radiated into the air by the resonator. Thus, such acoustic musical instrument can generate the continuous musical tone having the good sound quality in the sufficient tone volume.
For the above-mentioned reason, there is a need to embody the acoustic processing apparatus which can offer the acoustic characteristic as similar to that of the resonator of the acoustic musical instrument.
In general, the acoustic plate of the piano itself has the asymmetric structure, and position relationship between one string and acoustic plate is different from that between another string and acoustic plate. Thus, different resonance effect can be obtained with respect to the vibration of each string. In other words, it can be said that the resonant sound of each string is generated by the different acoustic process in the piano. Therefore, in order to embody the acoustic processing apparatus with accuracy, it is necessary to provide a plenty of resonance circuits each effecting the different acoustic process on each pitch. Thus, there is a problem in that such acoustic processing apparatus must require a large-scale circuit. Similarly, in the instruments other than the piano, the acoustic characteristic of the resonator must be differed with respect to each pitch. In order to reproduce the resonant sounds of the above-mentioned instruments with high fidelity, it is desirable to effect the different acoustic process in response to each pitch.